"""SVSPR wrapper around the trained RandomForest.

Public surface:
    - SVSPR class         : load + predict on DataFrame / DataFrame / single SV
    - score(vcf, ref)     : convenience for whole-VCF scoring (returns DataFrame)
    - classify(chrom, ...) : convenience for one SV (returns dict)
    - load_default()      : load the bundled model
"""
from __future__ import annotations

from pathlib import Path
from typing import Optional, Union

import numpy as np
import pandas as pd
import pickle

from .features import (SVCall, FEATURE_COLS, extract_one, extract_batch,
                       from_vcf, WINDOW)


_DEFAULT_MODEL_PATH = (Path(__file__).resolve().parent.parent / 'model' /
                       'svspr_v14_seq.pkl')


def _assign_tier(cs: float) -> str:
    # Thresholds match Methods 2.7.2 (manuscript). CS is uncalibrated; if you
    # apply isotonic/Platt calibration, re-derive these cutoffs on calibrated CS.
    if cs >= 0.9:
        return 'high'
    if cs >= 0.7:
        return 'moderate'
    if cs >= 0.5:
        return 'warning'
    return 'low'


class SVSPR:
    """SV-SPR confidence scorer.

    Parameters
    ----------
    model_path : str | Path | None
        Path to a pickled sklearn classifier. If None, the bundled
        svspr_v14_seq.pkl is loaded.
    feature_cols : list[str] | None
        Override the feature column ordering if the model was trained on
        a different set. Defaults to FEATURE_COLS.
    """

    def __init__(self, model_path: Optional[Union[str, Path]] = None,
                 feature_cols: Optional[list] = None):
        path = Path(model_path) if model_path else _DEFAULT_MODEL_PATH
        if not path.exists():
            raise FileNotFoundError(f'Model file not found: {path}')
        with open(path, 'rb') as f:
            obj = pickle.load(f)
        # The training pickle is a dict {model, features, ...} or a raw estimator.
        if isinstance(obj, dict):
            self.model = obj.get('model') or obj.get('estimator')
            cols = obj.get('features') or obj.get('feature_cols')
            self.feature_cols = feature_cols or cols or FEATURE_COLS
            self.metadata = {k: v for k, v in obj.items() if k != 'model'}
        else:
            self.model = obj
            self.feature_cols = feature_cols or FEATURE_COLS
            self.metadata = {}

    # ── Scoring methods ──────────────────────────────────────────────────────
    def _align(self, feat_df: pd.DataFrame) -> pd.DataFrame:
        """Map user-facing feature names to the model's expected names.

        The trained model uses legacy column names like 'svlen_abs_manta',
        'svtype_DEL_manta', etc. The feature extractor produces clean names
        like 'svlen_abs', 'svtype_DEL'. This method bridges the two.
        """
        df = feat_df.copy()
        # Add legacy aliases for any column the model expects but isn't present.
        aliases = {'svlen_abs_manta': 'svlen_abs',
                   'svtype_DEL_manta': 'svtype_DEL',
                   'svtype_INS_manta': 'svtype_INS',
                   'svtype_DUP_manta': 'svtype_DUP',
                   'svtype_BND_manta': 'svtype_BND'}
        for legacy, clean in aliases.items():
            if legacy not in df.columns and clean in df.columns:
                df[legacy] = df[clean]
        return df.reindex(columns=self.feature_cols).fillna(0)

    def predict_df(self, feat_df: pd.DataFrame) -> pd.DataFrame:
        """Score a feature DataFrame. Adds CS and tier columns."""
        X = self._align(feat_df)
        cs = self.model.predict_proba(X.values)[:, 1]
        out = feat_df.copy()
        out['CS'] = cs
        out['tier'] = [_assign_tier(v) for v in cs]
        return out

    def predict_vcf(self, vcf_path: str, ref_path: str) -> pd.DataFrame:
        """Score every SV in a VCF. Returns DataFrame with coord + CS + tier."""
        feat_df = from_vcf(vcf_path, ref_path)
        return self.predict_df(feat_df)

    def predict_one(self, chrom: str, pos: int, end: int, svtype: str,
                    svlen: int, total_alt_support: float, ref_path: str
                    ) -> dict:
        """Score one SV call. Returns {'CS': float, 'tier': str}."""
        import pysam
        fa = pysam.FastaFile(ref_path)
        try:
            call = SVCall(chrom=chrom, pos=pos, end=end, svtype=svtype,
                          svlen=svlen, total_alt_support=total_alt_support)
            row = extract_one(call, fa)
        finally:
            fa.close()
        X = self._align(pd.DataFrame([row]))
        cs = float(self.model.predict_proba(X.values)[0, 1])
        return {'CS': cs, 'tier': _assign_tier(cs)}


# ── Module-level convenience functions ───────────────────────────────────────
_DEFAULT: Optional[SVSPR] = None


def load_default() -> SVSPR:
    """Return a cached SVSPR loaded from the bundled default weights."""
    global _DEFAULT
    if _DEFAULT is None:
        _DEFAULT = SVSPR()
    return _DEFAULT


def score(vcf_path: str, ref_path: str,
          model_path: Optional[str] = None) -> pd.DataFrame:
    """One-call API: score every SV in a VCF and return a DataFrame.

    Returns columns: chrom, pos, end, svtype, svlen, CS, tier, plus the 11
    feature columns used by the model.
    """
    model = SVSPR(model_path) if model_path else load_default()
    return model.predict_vcf(vcf_path, ref_path)


def classify(chrom: str, pos: int, end: int, svtype: str, svlen: int,
             total_alt_support: float, ref_path: str,
             model_path: Optional[str] = None) -> dict:
    """One-call API: classify a single SV. Returns {'CS': ..., 'tier': ...}."""
    model = SVSPR(model_path) if model_path else load_default()
    return model.predict_one(chrom, pos, end, svtype, svlen,
                             total_alt_support, ref_path)